I. Field of the Invention
This invention relates to an object locating or tracking system or process in which a vector field which is caused to nutate about an axis called the pointing vector, is used to locate or track a remote object. More particularly, the invention relates to such a system or process which is capable of transforming error components of translation and of angular orientation of a remote object from one coordinate frame into another coordinate frame.
II. Description of the Prior Art
The use of orthogonal coils for generating and sensing magnetic fields is well known and has been used in locating and tracking remote objects. For example, U.S. Pat. No. 3,644,825 teaches generating and sensing coils which move with respect to each other. Alternatively, the magnetic field can be made to rotate as taught in Kalmus, "A New Guiding and Tracking System", IRE Transactions on Aerospace and Navigational Electronics, March 1962, pages 7 through 10.
The use of coordinate transformers to determine the orientation of a first coordinate system with respect to a second coordinate system is well known. For example, U.S. Pat. Nos. 3,474,241 and 3,660,648 disclose transformers which transform angular rates or angular errors measured in a first coordinate frame into angular rates defined about the axes of an intermediate coordinate frame about whose axes the angular rotations or rates are defined and then integrate to determine the angles defining the angle-axis sequence which defines the orientation of the first coordinate frame with respect to a second coordinate frame through the use of Euler angles.
There still remains a need for a way to determine continuously the three errors in the angular orientation of and the two errors in the pointing angles to a remote object in a manner suitable for directly correcting the presumed values of the five angles in addition just to locating or tracking the object. Further, there is a need for a coordinate transformer capable of transforming error components of a translation displacement, as well as an angular orientation displacement, of a remote object from one coordinate frame into another coordinate frame. Such coordinate transformation is not only useful in providing accurate tracking and orientation determination of the remote object but is necessary for providing accurately sensed error information about the pointing to and the orientation of the object relative to a useful coordinate frame, regardless of the attitude assumed by the object.